Re: [PATCH v6 perf, bpf-next 1/7] perf, bpf: Introduce PERF_RECORD_KSYMBOL

From: Song Liu
Date: Thu Jan 10 2019 - 14:47:12 EST




> On Jan 10, 2019, at 11:30 AM, Song Liu <songliubraving@xxxxxx> wrote:
>
>
>
>> On Jan 10, 2019, at 10:55 AM, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>>
>> Em Thu, Jan 10, 2019 at 06:40:37PM +0000, Song Liu escreveu:
>>>
>>>
>>>> On Jan 10, 2019, at 10:24 AM, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>>>>
>>>> Em Wed, Jan 09, 2019 at 11:21:05AM -0800, Song Liu escreveu:
>>>>> For better performance analysis of dynamically JITed and loaded kernel
>>>>> functions, such as BPF programs, this patch introduces
>>>>> PERF_RECORD_KSYMBOL, a new perf_event_type that exposes kernel symbol
>>>>> register/unregister information to user space.
>>>>>
>>>>> The following data structure is used for PERF_RECORD_KSYMBOL.
>>>>>
>>>>> /*
>>>>> * struct {
>>>>> * struct perf_event_header header;
>>>>> * u64 addr;
>>>>> * u32 len;
>>>>> * u16 ksym_type;
>>>>> * u16 flags;
>>>>> * char name[];
>>>>> * struct sample_id sample_id;
>>>>> * };
>>>>> */
>>>>
>>>> So, I couldn't find where this gets used, the intention here is just to
>>>> add the interfaces and afterwards is that you will wire this up? I would
>>>> like to test the whole shebang to see it working.
>>>
>>> I guess you meant PERF_RECORD_BPF_EVENT not being used?
>>>
>>> PERF_RECORD_KSYMBOL is used by BPF in 3/7 and 5/7. I tested
>>
>> Oops, I didn't look at 3/7, just read its cset summary line and as it
>> says:
>>
>> Subject: [PATCH v6 perf, bpf-next 3/7] perf, bpf: introduce PERF_RECORD_BPF_EVENT
>>
>> I didn't thought it was related, perhaps break it down into one that
>> states that it is wiring up PERF_RECORD_KSYMBOL, and at that point we
>> could just test it, getting the notifications for new kallsyms related
>> to BPF?
>
> Good idea! I will split it into two patches as:
>
> [3/8] perf, bpf: generate PERF_RECORD_KSYMBOL for BPF program
> [4/8] perf, bpf: introduce PERF_RECORD_BPF_EVENT
>
>>
>>> PERF_RECORD_BPF_EVENT with dump_trace. As we separate RECORD_KSYMBOL from
>>> RECORD_BPF_EVENT, user space won't use BPF_EVENT until annotation support.
>>
>> Right, so why not just introduce PERF_RECORD_KSYMBOL, make it be used by
>> tooling, etc, then move on to PERF_RECORD_BPF_EVENT?
>
> I'd like to make sure we all agree on the new ABI for RECORD_KSYMBOL and
> RECORD_BPF_EVENT. Multiple user space tools dependent on RECORD_BPF_EVENT,
> for example, bcc and auditing. Finalizing RECORD_BPF_EVENT will unblock the
> development of these tools. On perf side, it will take us quite some time
> to finish annotation. Ideally, I don't want to block the development of
> other tools for so long.
>
> Thanks,
> Song

+ DavidA

Hi David,

Could you please share your feedback on PERF_RECORD_BPF_EVENT for auditing
use cases?

Thanks,
Song